The invention relates to the delivery of digital content in data networks, especially in mobile data networks.
Communication infrastructures suitable for mobile users (in particular, though not exclusively, cellular radio infrastructures) have now become widely adopted. Whilst the primary driver has been mobile telephony, the desire to implement mobile data-based services over these infrastructures, has led to the rapid development of data-capable bearer services across such infrastructures. This has opened up the possibility of many Internet-based services being available to mobile users. Mobile data networks, such as GPRS networks, are therefore becoming more widely implemented.
One issue with such networks is that they often employ a relatively small number of centralised gateway elements for access to other networks, such as the public internet. The role of such gateways is typically to act as a router serving all the IP addresses of the mobile stations, but this node may also include firewall, packet filtering, mobility management and charging functions that can usefully be centralised.
For instance, GPRS networks employ an element known as a Gateway GPRS Support Node (GGSN) through which all IP traffic to and from an external IP network, such as the public internet, must normally pass. The GGSNs generally connect to the public internet via a set of servers that protect the operator network, participate in the internet routing or start secure channels towards enterprise networks, for instance.
In parallel with such developments, content delivery systems are being built that deliver over fixed IP infrastructures rich media content, such as video, audio, documents, games or the like, to end users using wide area data networks, such as the public internet or corporate networks and content delivery protocols such as http, RTSP, SIP, or RTP, for instance. In order to make more efficient use of network bandwidth and to increase the quality of service, such content delivery systems are often arranged to distribute the content using servers that can serve user requests for content delivery as locally as possible. These servers are generally content delivery servers that are usually distributed at the edge of an IP core network and are thus generally referred to as edge servers. A mechanism is then provided for directing or forwarding end user requests for particular content items to a selected edge server based on various criteria such as geographical location, server availability and load, content availability or the like. In such systems, the edge servers are typically interconnected together via an IP network for automatic management of the devices and their content.